Cokin P477 77mm P-Series Adapter Ring
One ring to rule your lens.
Available in most popular diameters, ring is the passport for creativity. All you need is to find the filter diameter of your lens. Most of the time, it is written on the front of the lens itself. If not, check the lens user manual. Then, just screw the ring on the front thread of your lens, and you're done! If you have lenses of different diameters, the only thing you need to change is the ring. It's very economical!